Power of shared pain triggers extreme self-sacrifice

The extreme self-sacrificial behavior found in suicide bombers and soldiers presents an evolutionary puzzle: how can a trait that calls for an individual to make the ultimate sacrifice, especially in defense of a group of non-kin, persist over evolutionary time?

A new study from the National Institute for Mathematical and Biological Synthesis (NIMBioS), based at the University of Tennessee, Knoxville, provides some answers, lending insight into the causes of self-sacrifice in violent conflicts around the world from holy wars to gangland violence.

The study, published today in Nature's Scientific Reports, found that sharing strong negative experiences can enable extreme cooperation in a group and, under some conditions, cause in individuals a willingness to die for the sake of the group. The researchers theorized that human evolution explains the origin of this visceral bonding over shared painful experiences, leading to an extreme type of cooperation.

The research draws on a large body of experimental evidence that suggests willingness to fight and die for a group may be motivated by what is called "identity fusion," where personal and social identities blur, producing a sense of oneness with the group that can transcend even the bonds of kinship.

The research was conducted by a team of international researchers from UT, NIMBioS, the University of Oxford, the University of Melbourne, Australia, National University of Distance Education, Madrid, Spain, Queen's University, Belfast, the University of London and RAND Corporation.

The researchers were interested in what causes identity fusion and wanted to test preliminary psychological evidence suggesting that one powerful cause of identity fusion is sharing dysphoric—painful and frightening—experiences.

They proposed that willingness to perform costly acts for the group is a behavioral strategy that evolved in human ancestors to enable success in high-risk collective activities and between-group conflicts. Groups whose members fused together after sharing painful experiences would be more likely to prevail in between-group conflicts, whereas ancestral groups that did not fuse would be less likely to survive. In modern groups, the willingness to sacrifice for the group would be expressed only under extreme conditions, the researchers surmised.

The study used mathematical models to generate a series of hypotheses tested in experiments.

"Using a mathematical modeling approach to explain this problem enabled us to develop new insights and knowledge that was not accessible before," said co-author Sergey Gavrilets, a UT professor of ecology and evolutionary biology and mathematics and NIMBioS associate director for scientific activities.

There were five hypotheses: shared experience promotes willingness to perform extreme pro-group action; shared negative experiences make individuals contribute more than euphoric experiences; the more intense the experience the stronger the pro-social effects; the effect of shared negative experiences on pro-social behavior is much stronger where groups compete directly against other groups rather than if they cooperate against nature; and the effects of shared negative experience can be stronger than those of kinship.

The hypotheses were then tested empirically in a variety of different study populations, including U.S. military veterans of the Vietnam war, college fraternity and sorority members who had undergone hazing, English Premier League football fans, martial arts practitioners of Brazilian Jiu Jitsu who sometimes use painful belt-whipping, and twins to examine the level of fusion.

From both the theoretical and empirical research, the study concluded that overall shared negative experiences are a powerful mechanism for promoting pro-social behaviors, which under certain conditions can be extremely costly to the individuals concerned.

The models were intended to capture the conditions faced by human ancestors tens of thousands of years ago. The researchers speculated that under threatening conditions, having a shared evolutionary future likely was a more decisive factor in cooperation and self-sacrifice than shared ancestry. Adaptation and survival was particularly difficult during the Late Pleistocene more than 100,000 years ago, they noted, when the environment was highly variable and when competition for limited resources was high.

"While previous research in evolutionary biology has identified a number of paths for the evolution of cooperation, this study introduces a novel, previously under-appreciated but very powerful mechanism: conditioning acts of extreme cooperation on shared prior experience," UT's Gavrilets said.

In the study, the new mechanism was evident beyond the effects of group performance or the effects of kinship on cooperation, he said.

Gavrilets noted the common expression "band of brothers" describing military and other units engaged in violent conflict. "Shared dysphoric experiences can make individuals feel even closer than brothers," he said.

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20 comments

Odd study with a tenuous conclusion. Certainly, shared dysphoric experiences might be expected to cause group bonding and lead to personal sacrifice for the group. Other factors can also be expected to lead to group bonding and personal sacrifice -- comradery, love, pride, etc.

None of this explains the suicidal mass murder of people who pose no threat to the group such as seen with Muslim terrorist groups. Nor does it explain the lone suicide murderer who identifies with a group but has never had the opportunity to be a part of or bond with the group.

From both the theoretical and empirical research, the study concluded that overall shared negative experiences are a powerful mechanism for promoting pro-social behaviors, which under certain conditions can be extremely costly to the individuals concerned.

I can't somehow imagine some particular situation, to which such a theory could be applied. For example the mass suicides in sectarian communities weren't consequence of some extraordinary suffering of their peers. Should for example the hard military drill promote more prosocial behavior of soldiers?

"There can be no doubt that a tribe including many members who, from possessing in a high degree the spirit of patriotism, fidelity, obedience, courage, and sympathy, were always ready to give aid to each other and to sacrifice themselves for the common good, would be victorious over most other tribes; and this would be natural selection" Darwin, 1871

-and the tribal dynamic...

"A life of constant external enmity generates a code in which aggression, conquest and revenge, are inculcated, while peaceful occupations are reprobated. Conversely a life of settled internal amity generates a code inculcating the virtues conducing to a harmonious co-operation" Spencer, 1892

None of this explains the suicidal mass murder of people who pose no threat to the group

Dog, you more than most should understand the value of martyrdom. It is the central theme of the NT. Jesus presented himself for killing and the saints all did the same thing.

Intratribal amity in conjunction with intertribal emnity meant consistent success in competition over resources. This is group selection at its best.

The quotes i cited are from the essay "Human Evolution and the Origin of War: A Darwinian heritageDennen, J. M. G. V. D. 1999", available for free download.http://www.rug.nl...7f).html

-I wish I could post the whole thing because it is exactly what the authors above are talking about. Darwin, spencer, lamark, bagehot, malthus, and many others all reached the same conclusions regarding tribalism and the emergence and development of the human race.

Religions are the institutionalization and codification of the tribal dynamic. They all teach altruism toward believers and animosity toward heathens, infidels, and apostates. They ALL demand suffering and sacrifice for the good of the group in return for immortality, absolution, retribution, and all wishes granted.

It is the central theme of the NT. Jesus presented himself for killing and the saints all did the same thing

But this is the reversed causality: the Jesus was an individual, who was supposed to increase the social cohesion of Christians by his personal sacrifice. Whereas the above study considers, that his sacrifice has been induced by dysphoric experiences of Christians - i.e. it has it exactly the opposite. BTW Learn to Write Badly: How to Succeed in the Social Sciences

I don't know anyone but you who could confuse martyrdom with mass murder

Martyrdom is obviously mass suicide. Those who encourage it, including the people who wrote your book, are mass murderers.

Your hatred for God blinds you

Your selfish desire to live forever in gods bosom blinds you to the realities of your religion. Theyre all the same in what they compel people to DO.

increase the social cohesion of Christians by his personal sacrifice

?? I dont know what youre trying to say here. The surviving religions all mastered the tribal dynamic for the purpose of outgrowing and overrunning. They were the best at convincing believers to suffer, sacrifice, and slaughter for their cause.

They all exterminated their weaker and less prolific adversaries, and they cannot help but continue the tradition today. Which is why we are all going to die unless they are stopped.

Jesus was an individual, who was supposed to increase the social cohesion of Christians by his personal sacrifice

We humans are supposedly so foul and corrupt that god had to murder his own son. And we are supposed to feel so guilty about it that we have to do the same with ourselves and our families in order to atone for it.

But how we feel about this sorry fable is immaterial. What we do because if it - whether it be sacrificing comfort, security, and repro rights to fight and die on the battlefield or simply not spending money in stores run by heathens - is what is important.

I don't know anyone but you who could confuse martyrdom with mass murder.

-Of course you do. You yourself would equate the 2 with jihadists. The question is why you would fail to recognize similar behavior in your own religion throughout history.

Your holy books all demand the same thing.

Re the article, tribalism explains what theyre talking about. Its biological. Science has been skirting the issue but cant yet acknowledge the fact because of all the unfortunate implications; that bigotry is natural for instance.

how can a trait that calls for an individual to make the ultimate sacrifice, especially in defense of a group of non-kin, persist over evolutionary time?

Since it's not an evolved trait but an induced behavior I think that's the wrong question to ask. the behaviopr does not 'persist'. It is created anew in each individual.

It's a bit like teaching Relativity. Understanding Relativity is not an evolved trait. It is something that must be taught and understood by each individual in turn. In both cases (suicide bombing and understanding Relativity) there is a perceived benefit to the individual (deeper understanding or 72 slave-virgins repectively...boy, are they surprised each time they find out their 72 virgins are male, tho). So maybe we're not dealing with 'social fusion' but rather with purely egoistic motives?

Our intelligence and environment has progressed far beyond the level that existed when the majority of our evoltion took place. As such we are now acting upon behaviours, social situations and mental health issues which evolution has had no where near a long enough time to weed out the disadvantageous. General suicide for no benefit of any group or cause is a clear example of this.

What the researcher dare not say here (because it would be unscientific) is that those who willingly die for the good of others, also have beliefs in the after-life, with certain advantages there if the personal sacrfice was for a good cause.

Microcompassion,Actually, it is scientific to acknowledge anything which is germane to the subject being studied. To ignore reality would be unscientific.

Your comment presumes all instances of someone willingly dying for someone else must be predicated on a belief by the person dying that their sacrifice will result in gain in some afterlife. That may certainly be true in some instances but certainly not all instances. Altruistic behaviors are observed in people who appear to have no particular religion or religiousness.

Your comment presumes all instances of someone willingly dying for someone else must be predicated on a belief by the person dying that their sacrifice will result in gain in some afterlife. That may certainly be true in some instances but certainly not all instances. Altruistic behaviors are observed in people who appear to have no particular religion or religiousness

?? What a surprisingly agnostic sentiment. I guess consorting here with the science-minded has corrupted your religionist sensibilities to some extent.

those who willingly die for the good of others, also have beliefs in the after-life

Some die for selfish reasons. Some would die (for any cause) if it also means escaping some debilitating physical or psychological pain. Some would die for their children. Some would die for their nation (Kamikaze?)Having a religious belief isn't a necessary prerequisite to blow yourself up for some cause. It's just one of many reasons.